Numerical Model for Nozzle Flow Application under LOX/Methane Hot Flow Conditions

Kurzfassung

A numerical study is conducted to investigate the impact of different chemical reaction mechanisms on the behavior of reactive nozzle flow. Therefore, a 66-step chemical reaction mechanism for oxygen/methane combustion is implemented into German Aerospace Center’s flow solver TAU. Ignition delay simulations are conducted and compared to experimental data to demonstrate the validity of this implementation. The implemented 66-step baseline chemistry model is applied for generic nozzle flow simulations, and the results are compared to frozen nozzle flow and nozzle flow in chemical equilibrium in order to investigate the impact of the finite-rate approach. The 66-step baseline reaction mechanism is reduced to a seven-step basic configuration, which is applied to the generic nozzle flow. A good agreement of the 66-step and the seven-step model is observed. Both approaches are applied for Reynolds-averaged Navier–Stokes simulations of a dual-bell nozzle hot-gas flow. Almost no deviation between the 66-step baseline model and the reduced chemical seven-step approach is observed. The dual-bell transition behavior at different values of combustion chamber mixture ratio is investigated, applying Reynolds-averaged Navier–Stokes simulations with a reduced chemistry model. Validation data for the simulations are obtained during a hot-flow test campaign. The experimentally observed impact of the combustion chamber mixture ratio on the dual-bell transition nozzle pressure ratio is clearly reproduced by the numerical approach. A good agreement with the experimentally obtained, transition nozzle pressure ratio values is reached by the numerical simulations. A reduction of 93% of the computational cost is observed due to the reduction of the chemical reaction mechanism.